Device and method for determining parameters of blind voids

ABSTRACT

Device for determining the size of a blind void comprises an elongated rigid rod, an actuator slidably movable relative to the rod, the actuator having a distal end for insertion into the void, a distal flexible element fixed at one end thereof to the rod, a second flexible element fixed at one end thereof to the rod and proximally removed from the distal flexible element. Movement of the actuator is operative to cause equal movements of the distal end portions of the distal and proximal elements, to cause the distal element to bulge outwardly from the rod to engage interior walls of the void and to cause the proximal element to bulge outwardly in a configuration duplicative of the distal element bulge, the proximal element being outside of the void and subject to observation.

REFERENCE TO PENDING PRIOR PATENT APPLICATION

[0001] This patent application claims benefit of pending prior U.S.Provisional Patent Application Serial No. 60/215,486, filed 06/30/00 byLehmann K. Li for REMOTE MEASURING APPARATUS AND METHOD, which patentapplication is hereby incorporated herein by reference.

FIELD OF THE INVENTION

[0002] This invention relates to the field of surgical devices usedprimarily for the repair or replacement of human tissue, including, butnot limited to, the nucleus pulposus of the spine. The invention furtherrelates to the method of using such devices.

BACKGROUND OF THE INVENTION

[0003] The spinal column is a flexible chain of closely linked vertebralbodies. In a normal human spine there are seven cervical, twelvethoracic and five lumbar vertebral bodies. Below the lumbar vertebraeare the sacrum and coccyx. Each individual vertebra has an outer shellof hard, dense bone. Inside the vertebra is a honeycomb of cancellousbone containing red bone marrow. All of the red blood cells and many ofthe white blood cells are generated inside this cancellous bone, wherethe blood cells mature before being released into the blood circulation.

[0004] The spinal disc serves as a cushion between the vertebral bodiesto permit controlled motion. A healthy disc consists of threecomponents: a gelatinous inner core called the nucleus pulposus; aseries of overlapping and laminated plies of tough fibrous rings calledthe annulus fibrosus; and two superior and inferior thin cartilagelayers, connecting the disc to the thin cortical bone of the vertebralbodies, called the endplates.

[0005] The spinal disc may be displaced or damaged due to trauma ordisease, such as a herniation or degenerative disc disease.

[0006] A herniated disc may bulge out and compress itself onto a nerve,resulting in lower leg pain, loss of muscle control, or paralysis. Totreat a herniated disc, the offending nucleus portions are generallyremoved surgically.

[0007] Disc degeneration gradually reduces disc height, forcing theannulus to buckle, tear or separate radially or circumferentially, andcausing persistent and disabling back pain. Degenerative disc disease isgenerally treated presently by surgically removing the nucleus andfusing the adjacent vertebral bodies to stabilize the joint.

[0008] In either case, whether removing a portion of the nucleus or allof the nucleus, these procedures ultimately place greater stress onadjacent discs to compensate for the lack of motion, which may causepremature degeneration of those adjacent discs.

[0009] Modern trends in surgery include the restoration of bodilyfunction and form (i.e., repair) of anatomical structures through theuse of minimally invasive surgical techniques. The ability to surgicallyrepair damaged tissues or joints, creating as few and as small incisionsas possible, produces less trauma, less pain and better clinicaloutcomes in general.

[0010] An emerging technique to treat degenerative disc disease is toreplace the degenerated nucleus with a prosthetic nucleus in an attemptto restore function, versus fusion which severely limits the function ofthe spine. Since a degenerated nucleus can be removed using relativelysmall diameter instruments (e.g. 5 mm or less), this approach is moreconducive to minimally invasive techniques.

[0011] A deficiency of current minimally invasive surgical techniques toreplace the nucleus is the difficulty in determining whether enoughspace in the disc has been created to properly fit an implant. Creatingthe proper dimension cavity may be particularly important whenimplanting a device that expands, such as with a hydrogel implant. Ifthe cavity created is larger than the implant, unintended implantmovement or instability can occur. If the cavity created is smaller thanthe implant, an implant either may not fit, may not be positionedcorrectly or an expandable device may not achieve its proper functionalshape.

SUMMARY OF THE INVENTION

[0012] It is, therefore, one object of the present invention to providea device and method for determining how much space is created in humantissue, particularly when the space is in a visually impaired location.

[0013] A further object of the invention is to provide a device andmethod for determining how much space is created in the inner portion ofthe intervertebral disc space to facilitate the implantation of anartificial nucleus pulposus. The present invention is adapted to beplaced through a small opening created in the annulus to minimize traumato surrounding tissue.

[0014] With the above and other objects in view, a feature of theinvention is the provision of a device for determining parameters of ablind void. The device comprises an elongated rigid rod, and an actuatorextending lengthwise of the rod and slidably movable relative to therod, the actuator having a distal end for insertion into the void. Afirst flexible element is fixed at one end thereof to the rod proximatethe distal end of the rod. A second flexible element is fixed at one endthereof to the rod and proximally removed from the distal end of the rodand from the first element. Movement of the actuator is operative tocause equal movements of the distal end portions of the first and secondelements, to cause the first element to bulge outwardly from the rod toengage interior walls of the void and to cause the second element tobulge outwardly in a configuration substantially duplicative of thefirst element bulge, the second element being outside of the void andsubject to observation.

[0015] In accordance with a further feature of the invention, there isprovided a method for determining parameters of a blind void, the methodcomprising the steps of providing a device comprising an elongated rigidrod, a first flexible element fixed at one end thereof to the rodproximate a distal end of the rod, a second flexible element fixed atone end thereof to the rod and proximally removed from the distal end ofthe rod and from the first element, and an actuator extending lengthwiseof the rod and engageable with distal end portions of the first andsecond elements. The method further includes the steps of inserting thedistal end of the actuator and the first element into the void, movingthe actuator to cause movements of the distal end portions of the firstand second elements, to cause the first element to bulge outwardly toengage interior walls of the void, and to cause the second element tobulge outwardly in a configuration duplicative of the first elementbulge, the second element being outside of the void, and determiningfrom the size of the second element the size of the first element andthereby the void.

[0016] The above and other features of the invention, including variousnovel details of construction and combinations of parts and methodsteps, will now be more particularly described with reference to theaccompanying drawings and pointed out in the claims. It will beunderstood that the particular device and method embodying the inventionare described by way of illustration only and not as limitations of theinvention. The principles and features of this invention may be employedin various and numerous embodiments without departing from the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Reference is made to the accompanying drawings in which is shownan illustrative embodiment of the invention, from which its novelfeatures and advantages will be apparent.

[0018] In the drawings:

[0019]FIG. 1 is a perspective view of one form of device illustrative ofan embodiment of the invention;

[0020]FIG. 2 is a diagrammatic top view of the device of FIG. 1 deployedin a spinal disc;

[0021]FIG. 3 is similar to FIG. 1, but shows the device in anotheroperative configuration; and

[0022]FIG. 4 is similar to FIG. 2, but shows the device in a parameterdetermining configuration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Referring to FIG. 1, it will be seen that an illustrativeinventive device 10 includes an elongated rigid rod 20, in the form ofat least one, and preferably two, plates 22. When the device includestwo plates, the plates extend parallel to each other.

[0024] An actuator 24 extends lengthwise of the rod 20 and is slidablymovable relative to the rod 20. When the rod 20 includes two plates 22,the actuator 24 is slidably disposed between the two plates.

[0025] A first flexible element, such as a strip 26, is fixed at aproximal end portion 28 thereof to the rod 20 proximate the distal end30 of the rod. The element 26 may be a bendable strip of metal having adistal free end 32. A first flexible element 26 is fixed to each of theplates 22.

[0026] Mounted on a distal end 34 of the actuator 24 is a firstengagement member 36 which is engageable with the distal end 32 of eachof the first elements 26. The first engagement member 36 may be anend-piece 38 fixed to the distal end 34 of the actuator 24.

[0027] A second flexible element, such as a strip 40, is fixed to eachof the plates 22 at a proximal end portion 42 of the element. Theelement 40 is of the same configuration, size and material as theelement 26 and is provided with a distal free end 44. A flexible secondelement 40 is fixed to each of the plates 22 proximally of the distalend 30 of the rod 20 and proximally of the first flexible element 26.

[0028] Mounted on each of the plates 22 on a side opposite from theactuator 24 is a second engagement member 50 connected to the actuator24 by a connecting pin 52. The second engagement member 50 may be ablock 54.

[0029] The rod 20 is provided with a grip portion 46 at the proximal end47 of the rod by which the rod may be gripped by an operator (notshown). The actuator 24 is provided with a manipulable portion, such asa cross-bar 48, such that an operator may hold the device 10 in one handby gripping the rod grip portion 46 and the actuator cross-bar 48, andby squeezing the cross-bar toward the grip portion, cause the actuatorto move proximally relative to the plates 22. The plates are eachprovided with a slot 56 through which extends a cross-bar portion, suchthat the cross-bar 48 may readily move relative to plates 22. Similarly,the plates 22 are each provided with a slot 58 through which extends theconnecting pin 52, permitting movement of the engagement block 54relative to the plates 22.

[0030] In operation, the device 10, as shown in FIG. 1, is inserted intoa void, such as a spinal disc cavity 60 from which the nucleus pulposushas been removed (FIG. 2). By manipulation of the rod grip portion 46and actuator cross-bar 48, the actuator 24 is made to move proximallyrelative to the rod 20. Proximal movement of the actuator 24 carrieswith it proximal movement of the end piece 38 and engagement block 54which, contacting the element free distal ends 32,44, respectively,cause proximal movement of the flexible element free ends 32,44, whilethe flexible element proximal ends 28,42 remain fast to their respectiveplates 22. The elements are thus caused to bulge outwardly (FIGS. 3 and4) until the first element 26 engages interior walls 62 of the cavity60, stopping movement of the actuator 24.

[0031] At this point, the first element 26 is hidden from view and theextent of the bulge is not ordinarily observable. However, because thesecond flexible element 40 is of the same configuration, size andmaterial as the first element and expands in a manner duplicating theexpansion of the first element, and is in an observable disposition, thesize of the spinal disc cavity may be determined by observation of thesecond element. While it is intended that “observation” includes visualobservation and mechanical measurement, it is apparent that“observation” can be undertaken by optical or automatic data gatheringinstruments in combination with computers and/or read-out devices.

[0032] It should also be appreciated that device 10 may be used todetermine cavity sizes in a variety of different directions. Thus, forexample, in FIGS. 2-4, device 10 is shown oriented so as to measurecavity size in a substantially horizontal direction. However, it shouldalso be appreciated that device 10 may be oriented, or modified, so asto measure cavity size in a substantially vertical direction, or in someother direction.

[0033] There is thus provided a device and method for determining thespace available in a blind void, and particularly in a spinal disccavity vacated by extraction of the nucleus pulposus therefrom.

[0034] It is to be understood that the present invention is by no meanslimited to the particular construction herein disclosed and/or shown inthe drawings, but also comprises any modification or equivalent withinthe scope of the claims.

What is claimed is:
 1. A device for determining parameters of a blindvoid, the device comprising: an elongated rigid rod; an actuatorextending lengthwise of said rod and slidably movable relative to saidrod, said actuator having a distal end for insertion into the void; afirst flexible element fixed at one end thereof to said rod proximatethe distal end of said rod; a second flexible element fixed at one endthereof to said rod and proximally removed from the distal end of saidrod and from said first element; wherein movement of said actuator isoperative to cause equal movements of the distal end portions of saidfirst and second elements, to cause said first element to bulgeoutwardly from said rod to engage interior walls of the void and tocause said second element to bulge outwardly in a configurationduplicative of said first element bulge, the second element beingoutside of the void and subject to observation.
 2. The device inaccordance with claim 1 wherein said actuator is engageable with distalend portions of said first and second elements to cause the movements ofsaid distal end portions of said elements and thereby the bulgingoutwardly of said elements.
 3. The device in accordance with claim 1wherein said actuator comprises an end piece fixed to the distal end ofsaid actuator and engageable with a distal end of said first flexibleelement, and a projection engageable with a distal end of said secondflexible element, such that the distal ends of the elements are movedtoward the fixed ends of the elements to cause portions of the elementsbetween the distal and fixed ends thereof to bulge outwardly.
 4. Thedevice in accordance with claim 1 wherein said rod is provided with agrip portion at a proximal end thereof and said actuator is providedwith a manipulable portion proximate a proximal end of said actuator andproximate the grip portion.
 5. The device in accordance with claim 1wherein said elements each comprise at least one strip of flexiblematerial.
 6. The device in accordance with claim 1 wherein said actuatorcomprises a rigid elongated member.
 7. A device for determiningparameters of a blind void, the device comprising: an elongated rodhaving a proximal end and a distal end; an actuator slidably mounted onsaid rod for movement distally and proximally on said rod; first andsecond flexible elements fixed to a surface of said rod opposite fromsaid actuator, said first flexible element being disposed at a distalend of said rod and said second flexible element being disposedproximally of said first element, said elements being substantiallyidentical to each other; first and second engagement members fixed tosaid actuator and engageable with distal ends of said first and secondelements, respectively; wherein proximal movement of said actuatorrelative to said rod causes said engagement members to contact thedistal ends of said elements to bulge said elements outwardly to producefirst and second identical bulges, one of the bulges being exposed forobservation.
 8. The device in accordance with claim 7 wherein said rodcomprises first and second plates of equal configuration and size andextending parallel to each other, and said actuator is slidably disposedbetween said first and second plates, each of said plates having thefirst and second flexible elements fixed thereon on outwardly facingwalls thereof, and the engagement members engage the distal ends of allof said flexible elements to cause bulging of all of said elementssimultaneously.
 9. The device in accordance with claim 8 wherein saidrod is provided with a grip portion at a proximal end thereof and saidactuator is provided with a manipulable portion proximate the gripportion, such that an operator can hold said rod and move said actuatorwith one hand.
 10. A device for determining the size of a spinal discvoid created by removal of nucleus pulposus, such that an artificialnucleus implant may be properly sized before attempted implantationthereof, the device comprising: an elongated rod; an actuator extendinglengthwise of said rod and slidably movable relative to said rod, saidactuator having a distal end for insertion into the disc void; a firstflexible element fixed at one end to said rod proximate a distal end ofsaid rod for insertion into the disc void; a second flexible elementfixed at one end to said rod and removed from said first element and thedistal end of said rod to remain outside of the disc void; andengagement members mounted on said actuator, each engagement member uponmovement of said actuator, being engageable with a free end of one ofsaid elements to bulge outwardly said first element in the disc void andto bulge outwardly said second element to the same extent as the firstelement, such that the bulge of the second element is available toinspection and replicates the bulge of said first element.
 11. Thedevice in accordance with claim 10 wherein said engagement memberscomprise an end piece fixed to a distal end of said actuator and a blockfixed to a side of said actuator, said end piece being engageable withthe free end of said first element to cause said first element to bulgeoutwardly in the disc void, and said block being engageable with thefree end of said second element to cause said second element to bulgeoutwardly.
 12. The device in accordance with claim 11 wherein said rodcomprises first and second plates extending parallel to each other, andsaid actuator comprises a plate slidably disposed between the rod firstand second plates.
 13. The device in accordance with claim 11 whereinsaid rod comprises two parallel plates and said actuator is disposedbetween said plates, said first flexible element being fixed on anoutwardly facing surface of a first of the plates, another firstflexible element being fixed on an outwardly facing surface of a secondof the plates, said end piece being engageable with the free ends ofboth first elements simultaneously, said second flexible element beingfixed on an outwardly facing surface of the first of the plates, anothersecond flexible element being fixed on an outwardly facing surface ofthe second of the plates, said block being disposed on an outwardlyfacing surface of the first plate, and another block being disposed onan outwardly facing surface of the second of the plates.
 14. The devicein accordance with claim 13 wherein said blocks are fixed to saidactuator by connecting pins which extend through slots in the plates.15. The device in accordance with claim 13 wherein said rod includes agrip portion at a proximal end of said rod, and said actuator includesmanipulation structure proximate the grip portion, such that the deviceis adapted to be held and operated by one hand of an operator.
 16. Thedevice in accordance with claim 15 wherein the manipulation structurecomprises a cross-bar extending width-wise of said said actuator andthrough slots in the plates.
 17. A method for determining parameters ofa blind void, the method comprising the steps of: providing a devicecomprising: an elongated rigid rod; a first flexible element fixed atone end thereof to said rod proximate a distal end of said rod; a secondflexible element fixed at one end thereof to said rod and proximallyremoved from the distal end of said rod and from said first element; andan acutator extending lengthwise of said rod and engageable with distalend portions of said first and second elements; inserting the distal endof said actuator and said first element into the void; moving saidactuator to cause movements of the distal end portions of said first andsecond elements, to cause said first element to bulge outwardly toengage interior walls of the void, and to cause said second element tobulge outwardly in a configuration duplicative of the first elementbulge, the second element being outside of the void; and determiningfrom the size of the second element the size of the first element andthereby the void.
 18. The method in accordance with claim 17 wherein:said device includes a grip portion disposed at a proximal end of saidrod, and a manipulable portion disposed on said actuator; and the stepof moving said actuator comprises squeezing the grip portion towards themanipulative portion.
 19. A method for determining the size of a spinaldisc void created by removal of nucleus pulposus, such that anartificial nucleus implant may be properly sized before attemptedimplantation thereof, the method comprising the steps of: providing adevice comprising: first and second plates disposed side by side andparallel to each other; a distal flexible element fixed at one endthereof to each of said plates; a proximal flexible element fixed at oneend thereof to each of said plates, said proximal elements beingproximally removed from said distal elements; and an actuator extendingslidably between said plates and having portions thereof engageable withfree distal end portions of said flexible elements; inserting a distalend of said actuator and said distal elements into the spinal disc void;moving said actuator to cause the actuator engageable portions to engagethe free distal end portions of said elements to cause said distalelements to bulge outwardly to engage interior walls of the void and tocause said proximal elements to bulge outwardly in a configurationduplicative of the distal elements' bulges, the proximal elements beingoutside of the void; and observing the size of the bulged proximalelements to determine the size of the bulged distal elements, andthereby the size of the void.
 20. The method in accordance with claim 19wherein observing the bulged proximal elements includes at least one ofvisual observation and automatic data gathering and read-out.
 21. Themethod in accordance with claim 19 wherein said actuator is oriented soas to determine the size of the void in a substantially horizontaldirection.
 22. The method in accordance with claim 19 wherein saidactuator is oriented so as to determine the size of the void in asubstantially vertical direction.